Human Error Blamed in Loss of Mars Global Surveyor

Mary O'Keefe

Having lost communication with Mars Global Surveyor late last year, JPL/NASA announced late last week that an internal board has determined the spacecraft was lost due to a series of events triggered after ground control in Denver sent an incorrect computer address.

"There was not a single thing that happened," said Fuk Li, Mars exploration program manager at JPL in La Cañada Flintridge. "It was a series of events that caused the problem."

MGS was launched in November 1996, and arrived at Mars to begin its mission in September 1997. It operated longer at Mars than any other spacecraft in history, more than four times its original prime mission. It last communicated with Earth on November 2, 2006, just days before its tenth anniversary.

JPL scientists and engineers continued their attempts to contact the spacecraft for days after the initial loss without success. The MGS team used resources like Spirit and Opportunity, the rovers on the Martian surface, as well as other spacecraft in the planet's orbit, but there was still no sign. An internal NASA board was formed to look into why the spacecraft went silent. The results were released April 13.

The board traced the problem back to a routine update relayed to the onboard MGS computers that caused inconsistencies in the spacecraft's memory.

"Then, later in November when we tried to move the solar panels, it tipped the spacecraft [toward the sun]," Li said.

When the spacecraft was ordered to perform a routine adjustment of its solar panels, a series of alarms were set off; however, the spacecraft later indicated it was stabilized. That was the last time ground control heard from MGS.

The board has determined that when that order was given, the spacecraft mistakenly turned its solar panel toward the sun that exposed its battery to direct sunlight.

"This made the battery warmer and warmer," Li said. "The spacecraft assumed that the battery was being charged."

Although the initial command was sent to the wrong location the board concluded that the MGS team followed existing procedures but those procedures were insufficient to catch the errors that occurred.

"That is one of the most important things, to try to understand what caused the problem and make changes to our project, our training and operation," Li said. "We will review all of this [data] and take action."

At this point however the whereabouts of the spacecraft is not known.

"We don't really know where the spacecraft is, [reviewing all the data] we think it is still in orbit around Mars," Li said.

According to Li, the original orbit for the spacecraft was 50 years; this means that it should be in orbit for another 40 years. He does not think that any other spacecrafts like Mars Reconnaissance Orbit or the Odyssey are in danger of crossing MGS's path.

"The other spacecrafts do not share the same orbit," Li said.

There have been attempts to photograph MGS by the other orbiting spacecrafts, and, during the first few weeks of its initial loss, the rovers attempted to receive some form of communication. All attempts were unsuccessful.

"We are in the final process of shutting the project down," Li said. The MGS mission at JPL will be laid off; most of the scientists and engineers have already moved on to other Mars missions, Li said.

The mission that sent back more than 200,000 photos of the Martian surface, helped map landing sites for future missions, and made historical findings of gullies and debris flow features that suggest current sources of liquid water at or near the surface of Mars, is now at an official end. MGS will circle the red planet as other, newer spacecraft continue the research.